The problem of circuits overheating is well known in the art. Typically, the circuits are tested to determine the maximum thermal conditions that the circuits can withstand and then appropriate cooling is provided, such as a fan, to prevent such a condition from occurring.
Computer circuitry is particularly susceptible to overheating and the computer may be occasionally used in conditions outside specified normal ranges. For example, ambient temperatures may exceed the specifications for the computer such as when air conditioning is temporarily out of order or collected dust and other contaminants may prevent the cooling fans from working properly. As a result, some form of heat detection such as a thermistor may be coupled to a fan to prevent the computer circuits from overheating by increasing the fan speed when the thermistor detects that the computer may be overheating. However, thermistors and many other types of analog sensors are subject to inaccuracies from unit variation and from degradation over time. As a result, some overheating conditions may not be detected by a thermistor.